Ray, You have beat me to the post on two accounts my friend: one was the UL42 - I was hoping to suggest using one of those but you swiftly got that one in - well done! The second one is, I own a Sunbeam radio (I thinks its model number is 57) that is bereft of it entire dropper. I feel it is safe to say that I have no option but to use a mains transformer - I’d like to get a tune out of it but getting hold of a circuit diagram is starting to prove more or less impossible. I plan to use this radio for a near future You Tube restoration series production with the idea of demonstrating that conversion is possible and then show how it is accomplished - I'll still do this. I’ve seen, some years ago, a transformer arrangement fitted in place of the droppers on a DAC90A. A fellow service tech’ used an autotransformer which, if my memory serves me correctly, salvaged from a scrap Bush, model AC thirty-something. When I get my Pye, model 49C, back from on loan as a prop to a local amateur theatre group, I’ll show photographs on You Tube of my rendition of converting an AC/DC radio to transformer AC only (it’s the only one I’ve ever done and it works well). I must say dear chap, before signing off, I really enjoyed watching this production - excellent way of showing how this is accomplished - well done. Regards, Phil.
Hi Phil, Great minds think alike! I'm glad you liked the video and I'm looking forward to your video. Thanks for taking the time to post, it's great to get feedback. Cheers, Ray.
I have been watching your vids here in the US. Very informative and a pleasure to watch ! I purchased a DAC90A and waiting on it to get here. In your vid you said you had to change a few things on the audio tube EL41 to El42 did not get all of it. I was wondering what the cathode resistor was replaced with from the 150ohm to ? and what was to modification on the audio output tube?
hi i was following your video as i find very interesting but i was confused when you said r13 going across the smoothing cap on my diagram i have r 15 going across and r 13 going to v4 can you clarify please thank you
You could use a time delay circuit for the HV if you chose to use diodes. Also, maybe some warm white LEDs for the dial light would save current draw even more. I know.....heresy :-)
Great video, I think that could also answer my question (at least partly) on modifying a British Bush for U.S. 120v mains voltage, using the correct transformer of course. Or go the other route and use an external step up transformer. Thanks, Tom
It looks like you have retained the half wave rectifier using a 1n4006. I'm wondering if the resulting DC imbalance on the secondary may be reducing the transformer efficiency and thus generating more heat. May be worth trying a bridge. Cheers Doug
Hello Ray. I am thankful that You have helped me before with an old radiogram chassis ( ruclips.net/video/slKaOyPjHqs/видео.html ). I have had a Bush DAC90 land on my bench and the mains dropper ballast resister look very worse for wear. Can I ask if it is possible to source a mains dropper for this please?
Hi Eddie, it's nice to hear from you. I'm afraid I can't help with the dropper as they are like hen's teeth these days. I think your only option will be to find a scrap radio to rob. Sorry about that. Cheers, Ray.
Hi there Ray. Thank you for your reply. Indeed, like pulling sharks teeth! :) Anyway I'm doing your mains transformer mod. Awesome!! I need a little more advice if that's OK. I'm at a point of refurbing the cabinet and cleaning the dial glass. I haven't touched it yet and I'm wondering if there is any useful tips about cleaning this. Any No-No's etc. Thank you Ray!
Hi Eddie, basically, don't clean the dial glass. Clean it very carefully, if it's really bad, but don't rub the lettering off. Try a little warm, soapy water but be careful.
Cheers Ray. I'll maybe upload this when I'm done. The Transformer mod is genius. I found one with separate winding for bulbs and centre tapped 6.3 volt winding. Awesome. Thanks again. :)
Bush should have done this at the time of manufacture instead of using this cheap and nasty and horrible ac dc tech. Anyway as i said the originality has been destroyed. The cost of a mt would have only increased the costs of a few bob.
The idea of the restoration of vintage Radios is to restore it to it´s original condition.This might not be 100% possible, but not to completely redesign the RX.
The cause of the overheating problem most likely won't be the heater current, but transformer saturation caused by the unipolar DC current flowing through the HT secondary caused by the half wave rectifier you are using. If you remove the half wave rectifier and replace it with a full wave type such as a 2W08M, then you'll probably find that the transformer will stay much cooler.
Hi Mark, It was difficult enough to find a 6.3 Volt transformer with enough current, let alone one of the correct voltage to supply the heaters in series. It was easier to change the valves to E series.
@@g4nsj ok! i am not a fan of modifications but i subscribed to your channel, you have a nice repair bench and i like your work. i also repair tube gear but i'm more into tv's ....cheers
Ray,
You have beat me to the post on two accounts my friend: one was the UL42 - I was hoping to suggest using one of those but you swiftly got that one in - well done! The second one is, I own a Sunbeam radio (I thinks its model number is 57) that is bereft of it entire dropper. I feel it is safe to say that I have no option but to use a mains transformer - I’d like to get a tune out of it but getting hold of a circuit diagram is starting to prove more or less impossible. I plan to use this radio for a near future You Tube restoration series production with the idea of demonstrating that conversion is possible and then show how it is accomplished - I'll still do this.
I’ve seen, some years ago, a transformer arrangement fitted in place of the droppers on a DAC90A. A fellow service tech’ used an autotransformer which, if my memory serves me correctly, salvaged from a scrap Bush, model AC thirty-something.
When I get my Pye, model 49C, back from on loan as a prop to a local amateur theatre group, I’ll show photographs on You Tube of my rendition of converting an AC/DC radio to transformer AC only (it’s the only one I’ve ever done and it works well).
I must say dear chap, before signing off, I really enjoyed watching this production - excellent way of showing how this is accomplished - well done.
Regards,
Phil.
Hi Phil,
Great minds think alike! I'm glad you liked the video and I'm looking forward to your video. Thanks for taking the time to post, it's great to get feedback. Cheers, Ray.
Interesting video, I think I would have been tempted to do an irreversible modification though....
Glad you did not resort to LED dial lights....
I have been watching your vids here in the US. Very informative and a pleasure to watch ! I purchased a DAC90A and waiting on it to get here. In your vid you said you had to change a few things on the audio tube EL41 to El42 did not get all of it. I was wondering what the cathode resistor was replaced with from the 150ohm to ? and what was to modification on the audio output tube?
hi i was following your video as i find very interesting but i was confused when you said r13 going across the smoothing cap on my diagram i have r 15 going across and r 13 going to v4 can you clarify please thank you
Hi Melvin,unfortunately some circuit diagrams vary. It’s confusing, I know. Which radio do you have?
@@g4nsj i have the dac 90a
Yes, there are at least two circuit diagrams which are the same apart from component numbers.
ok i have to be careful as to what i am looking at so i dont remove the wrong part thanks
@@g4nsj
Thanks to you , I learnt what a "Mains Dropper" is ! 👍🏻🇬🇧🏆👌🏻😎
Impressive Ray you really know your stuff.
Did Bush make them strange resistors in there radio's???
Kennynva which resistors?
Just curious how many ohms was the original dropper. Great video
The three sections are 150 - 150 - 950 ohms.
Thanks Ray!
You could use a time delay circuit for the HV if you chose to use diodes. Also, maybe some warm white LEDs for the dial light would save current draw even more. I know.....heresy :-)
+Don Lewis Hi Don, yes good idea. Cheers, Ray.
Great video, I think that could also answer my question (at least partly) on modifying a British Bush for U.S. 120v mains voltage, using the correct transformer of course. Or go the other route and use an external step up transformer.
Thanks,
Tom
Hi Tom, you should be able to find a suitable transformer and carry out the mod. Great stuff.
It looks like you have retained the half wave rectifier using a 1n4006. I'm wondering if the resulting DC imbalance on the secondary may be reducing the transformer efficiency and thus generating more heat. May be worth trying a bridge. Cheers Doug
Hi Doug, thanks for that. I did change it to a bridge as it also reduced hum. Thanks for commenting. Cheers, Ray.
I guess I needed to keep watching .. I got the rest of the info ... Thanks Ray !! wish me luck hopefully I can get it to work here !!
Hi Marty, sorry I didn't reply earlier but I've been away. Do keep me posted, I'd like to know how you get on. Cheers and good luck, Ray.
I thought the sence of restoring a Receiver was to restore it if possible to it´s original condition.
Graham Pinkerton it would take about 20 mins to put it back to original. 😀
Hello Ray. I am thankful that You have helped me before with an old radiogram chassis ( ruclips.net/video/slKaOyPjHqs/видео.html ). I have had a Bush DAC90 land on my bench and the mains dropper ballast resister look very worse for wear. Can I ask if it is possible to source a mains dropper for this please?
Hi Eddie, it's nice to hear from you. I'm afraid I can't help with the dropper as they are like hen's teeth these days. I think your only option will be to find a scrap radio to rob. Sorry about that. Cheers, Ray.
Hi there Ray. Thank you for your reply. Indeed, like pulling sharks teeth! :)
Anyway I'm doing your mains transformer mod. Awesome!!
I need a little more advice if that's OK. I'm at a point of refurbing the cabinet and cleaning the dial glass. I haven't touched it yet and I'm wondering if there is any useful tips about cleaning this. Any No-No's etc.
Thank you Ray!
Hi Eddie, basically, don't clean the dial glass. Clean it very carefully, if it's really bad, but don't rub the lettering off. Try a little warm, soapy water but be careful.
Cheers Ray. I'll maybe upload this when I'm done. The Transformer mod is genius. I found one with separate winding for bulbs and centre tapped 6.3 volt winding. Awesome. Thanks again. :)
What’s does the rectifier achieve/add to this setup?
Up Over Games it turns AC to DC.
Radio Workshop ah so you didn’t need it after you made the conversion?
LOOKS LIKE DANSETTE MAJOR TRANSFORMER .. jeff ..
Jeffrey petch-harrison I think it is, Jeff. Well spotted!
Modernization :-(
A temporary modification to show what can be done. It can be put back to original very easily. -:)
Well you have ruined the originality of the Receiver by changing the valves and putting in a mains Transformer.
Personally I think if it makes the radio safer then its a good idea.
Bush should have done this at the time of manufacture instead of using this cheap and nasty and horrible ac dc tech. Anyway as i said the originality has been destroyed. The cost of a mt would have only increased the costs of a few bob.
The radio has not been destroyed. It can be put back to original in about 20 minutes. I've kept the original parts. Cheers, Ray.
A slight mod? Now your joking.
The idea of the restoration of vintage Radios is to restore it to it´s original condition.This might not be 100% possible, but not to completely redesign the RX.
The cause of the overheating problem most likely won't be the heater current, but transformer saturation caused by the unipolar DC current flowing through the HT secondary caused by the half wave rectifier you are using. If you remove the half wave rectifier and replace it with a full wave type such as a 2W08M, then you'll probably find that the transformer will stay much cooler.
Thanks for that. I did use full wave in the end. Cheers, Ray.
Did that solve the overheating issue?
Magic Monty there was a slight improvement. Thanks.
Would you be able to work on an Armstrong ST3, by the way?
Hi, sorry I only deal with 1940s radios. Cheers, Ray.
U series valves don't have 6.3v heaters, may have been better to find a transformer with a secondary to run all heaters in series.
Hi Mark, It was difficult enough to find a 6.3 Volt transformer with enough current, let alone one of the correct voltage to supply the heaters in series. It was easier to change the valves to E series.
@@g4nsj Ah sorry, didn't realise you changed the valves too. That makes sense now :)
@@g4nsj 2 x12v transformers wired back to back making a 220 to 220 isolation setup wouldnt work? not enough space?
Hugo B. Not enough space, sadly.
@@g4nsj ok! i am not a fan of modifications but i subscribed to your channel, you have a nice repair bench and i like your work. i also repair tube gear but i'm more into tv's ....cheers